Method and apparatus of symmetrically chamfering substrate

ABSTRACT

A method of symmetrically chamfering a substrate includes repeating, at least a plurality of times, the steps of chamfering an edge of the substrate using a chamfering wheel, measuring an asymmetric chamfering deviation (y) of the edge of the substrate which is chamfered, and controlling a relative position of the chamfering wheel with respect to the substrate by a value of a function f(y) of the variable y. It is possible to constantly symmetrically chamfer the edge of the substrate via active response to a change in the chamfering environment without a hardware-based operation of the related art.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.14/287,799 filed on May 27, 2014 which claims priority from KoreanPatent Application No. 10-2013-0060306 filed on May 28, 2013, the entirecontents of each are incorporated herein for all purposes by thisreference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a method and apparatus of symmetricallychamfering a substrate, and more particularly, to a method and apparatusof symmetrically chamfering a substrate by measuring an asymmetricchamfering deviation of the substrate and controlling the position of achamfering wheel based on the asymmetric chamfering deviation.

Description of Related Art

In a plurality of fields, the edges of substrates are required to bechamfered. For instance, glass substrates which are used for flat paneldisplays, such as a liquid crystal display (LCD), a plasma display panel(PDP) and an electroluminescent (LE) display, can be manufactured bymelting, shaping, cutting and chamfering processes. That is, it ispossible to manufacture a glass substrate by melting a glass rawmaterial, shaping molten glass into a plate by solidifying it, cuttingthe glass plate according to a predetermined size, and chamfering edgesof the cut glass.

FIG. 1 is a schematic view showing the process of chamfering an edge ofa substrate 10, and FIG. 2 is a side cross-sectional view showing theedge of the substrate 10 which is asymmetrically chamfered.

The edge of the substrate 10 is chamfered in the state in which thesubstrate is placed on a chamfering table 30. Here, it is preferred thatthe edge of the substrate be chamfered symmetrically in the top-bottomdirection. However, since a glass substrate used, for example, for a PDPis thin (with a thickness of about 1 mm or less), a localizedmisalignment occurs between the center point of the cross-section at theedge of the substrate and the center point of a chamfering wheel 20 whenthe chamfering table is not flat or due to movement in the up and downdirection during carriage of the chamfering table. In this case, thecross-section of the edge is ground more deeply at one side, such thatthe chamfered width of the upper surface differs from the chamferedwidth of the undersurface. This consequently forms anasymmetrically-chamfered point on the edge of the substrate, i.e. alocalized area which is asymmetrically chamfered.

Traditionally, when the substrate is asymmetrically chamfered, anoperation of replacing a component of a device which fixes theasymmetrically-chamfered portion of the substrate or precisely adjustingthe local height of the chamfering table using a thin steel piece iscarried out. However, this operation requires a process of stopping thechamfering of the substrate and disassembling, reassembling andprecisely compensating the table, thereby causing massive damage toproductivity. This also has the problem of the increased cost due to thereplacement of the component.

The information disclosed in the Background of the Invention section isonly for better understanding of the background of the invention, andshould not be taken as an acknowledgment or any form of suggestion thatthis information forms a prior art that would already be known to aperson skilled in the art.

BRIEF SUMMARY OF THE INVENTION

Various aspects of the present invention provide a method and apparatusof symmetrically chamfering a substrate, which enables an edge of thesubstrate to be constantly symmetrically chamfered via active responseto a change in the chamfering environment without a hardware-basedoperation of the related art.

In an aspect of the present invention, provided is a method ofsymmetrically chamfering a substrate. The method includes repeating, atleast a plurality of times, the following steps of: chamfering an edgeof the substrate using a chamfering wheel; measuring an asymmetricchamfering deviation (y) of the edge of the substrate which ischamfered; and controlling a relative position of the chamfering wheelwith respect to the substrate by a value of a function f(y) of thevariable y.

In another aspect of the present invention, provided is an apparatus forsymmetrically chamfering a substrate that includes a chamfering wheelwhich chamfers an edge of the substrate at least a plurality of times; ameasuring part which measures an asymmetric chamfering deviation (y) ofthe edge of the substrate which is chamfered; and a controller whichcontrols the relative position of the chamfering wheel with respect tothe substrate by a value of a function f(y) of the variable y.

According to embodiments of the invention, it is possible to produce asymmetrically chamfered cross-section by automatically and constantlyaligning the height of the chamfering wheel with the center point of thecross-section of the edge of the substrate by replacing the method ofthe related art in which the center point of the cross-section at theedge of the substrate is aligned with the center point of the chamferingwheel by compensating a chamfering table on which the chamferingoperation is carried out. That is, the present invention has an effectin that the edge of the substrate can be constantly symmetricallychamfered via active response to a change in the chamfering environmentwithout the hardware-based operation of the related art. In particular,the invention makes it possible to promptly determine the degree ofdeterioration of the chamfering table which is continuously deterioratedby the repeated chamfering operation, and to directly take necessarymeasures.

In addition, the invention does not require stopping the chamferingoperation, and thus has an effect in that the edge of the substrate canbe symmetrically chamfered in a simple way without sacrificingproductivity.

Furthermore, the invention excludes labor and time loss which arerequired for the compensation of the chamfering table in the relatedart, thereby improving the efficiency of the chamfering process. Thatis, it is possible to obtain the maximum effect and significantlyincrease the level of distribution of the chamfered width whileminimizing the load of the operation. It is also possible tomass-produce chamfered substrates while maintaining the differencebetween the chamfered widths of the upper surface and undersurface ofthe substrate to a maximum of 30 μm or less (an average level of 20 μm)by operating a simple program when a worker on duty is not carrying outthe operation. The symmetry of chamfering was greatly improved over thecompensation technique of the related art from which the symmetry havinga difference between the chamfered widths of 50 μm or less cannot beobtained

The technique of measuring and compensating the degree of flatness ofthe chamfering table of the related art requires stopping the productionline, and is a dangerous operation which must be carried out in themiddle of equipment. In contrast, the invention can protect a workerfrom a dangerous environment.

The methods and apparatuses of the present invention have other featuresand advantages which will be apparent from, or are set forth in greaterdetail in the accompanying drawings, which are incorporated herein, andin the following Detailed Description of the Invention, which togetherserve to explain certain principles of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing the process of chamfering an edge ofa substrate;

FIG. 2 is a side cross-sectional view showing the edge of the substratewhich is asymmetrically chamfered;

FIG. 3 is a flow diagram depicting a method of symmetrically chamferinga substrate according to an embodiment of the invention;

FIG. 4 is a schematic view showing a plurality of measuring points onthe edges of a substrate;

FIG. 5 is a side cross-sectional view showing an asymmetric chamferingdeviation on one edge of a substrate;

FIG. 6 is a view showing the chamfered width at the upper surface andthe chamfered width at the undersurface at each chamfering which iscarried out by a method of symmetrically chamfering a substrateaccording an embodiment of the invention;

FIG. 7 is a view showing the chamfered width at the upper surface, thechamfered width at the undersurface and an asymmetric chamferingdeviation before and after a substrate is symmetrically chamfered by themethod of symmetrically chamfering a substrate according an embodimentof the invention;

FIG. 8 is a view showing a decrease in the asymmetric chamferingdeviation before and after the method of symmetrically chamfering asubstrate according an embodiment of the invention is applied; and

FIG. 9 is a schematic view showing an apparatus of symmetricallychamfering a substrate according to an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to various embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings and described below, so that a person having ordinary skill inthe art to which the present invention relates can easily put thepresent invention into practice.

Throughout this document, reference should be made to the drawings, inwhich the same reference numerals and signs are used throughout thedifferent drawings to designate the same or similar components. In thefollowing description of the present invention, detailed descriptions ofknown functions and components incorporated herein will be omitted whenthey may make the subject matter of the present invention unclear.

FIG. 3 is a flow diagram depicting a method of symmetrically chamferinga substrate according to an embodiment of the invention, FIG. 4 is aschematic view showing a plurality of measuring points on the edges of asubstrate, and FIG. 5 is a side cross-sectional view showing anasymmetric chamfering deviation on one edge of a substrate.

The method of symmetrically chamfering a substrate according to theinvention repeats a chamfering step, a measuring step and a controllingstep at least a plurality of times.

At the chamfering step, an edge of the substrate is chamfered using achamfering wheel.

The substrate 10 is placed on a chamfering table 30. Herein, the terms“up (upward),” “down (downward),” “left” and “right” are used todescribe the positional relationship but not to indicate the absoluteposition with respect to the surface of the earth. Therefore, thedescription that the substrate 10 is positioned on or above thechamfering table 30 merely means that the substrate 10 is positioned ina direction that is designated to be upward from the chamfering table30, but the upward direction does not necessarily indicate that it facesaway from the surface of the earth. While the substrate 10 may be aglass substrate for a display device, the invention is not limitedthereto. The substrate 10 according to the invention can be made of anymaterial as long as the substrate is supposed to be chamfered.

The chamfering wheel 20 is made of a material that is more rigid thanthe substrate 10. When the object to be chamfered is the glass substrate10, the chamfering wheel 20 typically contains diamond grinding chips.In general, the chamfering wheel 20 is provided as a disk type. Concavegrooves are formed in the outer circumference of the chamfering wheel 20along the circumferential direction thereof. The inner sides of thegrooves abut against the edge of the substrate 10, thereby evenlychamfering the edge of the substrate 10. The chamfering wheel 20 isgrasped by a dedicated grinding machine and is thereby rotated at a highspeed.

In general, the substrate 10 is moved and the chamfering wheel 20 isrotated in position. However, this is not always required. For instance,the arrangement in which the substrate 10 is fixed and the chamferingwheel 20 is movable is possible, or the arrangement in which both thesubstrate 10 and the chamfering wheel 20 are movable is possible. Inresponse to the relative movement between the substrate 10 and thechamfering wheel 20, the chamfering wheel 20 chamfers the edge of thesubstrate 10 while moving along the edge.

At the measuring step, an asymmetric chamfering deviation (y) of theedge of the substrate is measured.

According to an exemplary embodiment, the asymmetric chamferingdeviation is measured from the difference between the widths of theupper surface and the undersurface of the chamfered substrate 10.However, the present invention is not limited thereto. For instance, itis possible to measure the asymmetric chamfering deviation by directlyinspecting the cross-section of the edge of the substrate 10 from theside. A variety of devices, such as a vision camera and a distancesensor, can be used to measure the asymmetric chamfering deviation.

It is preferred that an asymmetric chamfering deviation is measured fromeach of a plurality of points on the edge of the substrate. While FIG. 4shows that this measuring operation is carried out on all of four edges,this is not intended to be limiting. Only a limited number of edges canbe measured as required. For example, four vision cameras can be used inorder to measuring the four edges of the substrate.

At the controlling step, the relative position of the chamfering wheelwith respect to the substrate is controlled by the value of a functionf(y), where the variable y is the asymmetric chamfering deviation.

Typically, the position of the chamfering wheel that is to be controlledis the relative height of the chamfering wheel with respect to thesubstrate. As described above, it should be understood that the term“height” is used in order to describe the relative positionalrelationship but not to indicate the absolute position. In addition,while the relative position may be changed by moving the chamferingwheel up and/or down, this is not intended to be limiting. For instance,it is possible to move the substrate in the up and down direction whilefixing the chamfering wheel, or to move both the chamfering wheel andthe substrate.

For instance, since a glass plate is thin (with a thickness of about 1mm or less), it is bent along the shape of the upper surface of thechamfering table due to the flatness of the chamfering table and underthe influence of the weight of the glass plate. In that state, the glassplate closely adjoins the upper surface of the chamfering table.Therefore, when the chamfering table 30 is not flat, the center point ofthe cross-section at the edge of the substrate 10 is locally misalignedfrom the center point of the chamfering wheel 20. When the height of alocalized area of the chamfering table 30 is lower than a referenceheight, the center point of the edge of the substrate 10 is positionedlower than the center point of the chamfering wheel 20, as shown in FIG.5. In this case, the undersurface of the substrate is more chamferedthan the upper surface of the substrate, such that the chamfered widthof the undersurface becomes greater than the chamfered width of theupper surface. Accordingly, the relative height of the chamfering wheelwith respect to the substrate is controlled in the upward direction.

In contrast, when the local height of the chamfering table 30 is greaterthan the reference height, the local center point of the cross-sectionat the edge of the substrate 10 is positioned higher than the centerpoint of the chamfering wheel 20. In this case, the upper surface of thesubstrate is more chamfered than the undersurface of the substrate, suchthat the chamfered width of the upper surface becomes greater than thechamfered width of the undersurface. Accordingly, the relative height ofthe chamfering wheel with respect to the substrate is controlled in thedownward direction.

It is preferred that the controlling step individually controls thepositions of the chamfering wheel when chamfering a plurality of pointson the edge of the substrate, like the measuring step. While FIG. 6 andFIG. 7 show that this controlling operation is carried out on all of thefour edges, this is not intended to be limiting. The controllingoperation can be carried out on only a limited number of edges asrequired. For example, four chamfering wheels can be used in order tochamfer the four edges of the substrate.

After the relative position of the chamfering wheel 20 with respect tothe substrate 10 is changed, the foregoing steps, including thechamfering step, the measuring step and the controlling steps, arerepeated. While the edge of the same substrate 10 can be chamfered andmeasured again, it is preferable to use another substrate 10. That is,it is possible to chamfer and measure the edge of a plurality ofsubstrates 10 while controlling the relative position of a singlechamfering wheel 20 with respect to each of the substrates 10.

The number of repetitions can be designated in advance and inputted intoa program, or the process can be repeated until the asymmetricchamfering deviation (y) has a value within a designated range.Furthermore, the measuring and controlling steps can be constantlycarried out, i.e. limitlessly repeated, during the chamfering operation.

After the chamfering step, the degree of asymmetry of the cross-sectionat the edge of the substrate is measured, the asymmetric chamferingdeviation is fed back, an amount of control f(y) (e.g. f(y)=y*a) isgenerated by multiplying the deviation (y) with a predetermined constant(a), and the height of the chamfering wheel is precisely determined bythe amount of control. After this first cycle, the degree of asymmetryat the same point is measured, an amount of control is generated in thesame way, and the position of the chamfering wheel that was previouslyset is corrected by accumulating this amount of control. When thisseries of processes is continuously repeated, a deviation in thechamfered width which is continuously changed due to the precision ofcarriage caused by deterioration of the chamfering operation and due tothe flatness can be set to a minimum value.

FIG. 6 is a view showing the chamfered width at the upper surface andthe chamfered width at the undersurface at each chamfering which iscarried out by a method of symmetrically chamfering a substrateaccording an embodiment of the invention, FIG. 7 is a view showing thechamfered width at the upper surface, the chamfered width at theundersurface and an asymmetric chamfering deviation before and after asubstrate is symmetrically chamfered by the method of symmetricallychamfering a substrate according an embodiment of the invention, andFIG. 8 is a view showing a decrease in the asymmetric chamferingdeviation before and after the method of symmetrically chamfering asubstrate according an embodiment of the invention is applied.

As shown in the figures, it can be appreciated that symmetric chamferingon an edge of a substrate was realized by repeating the chamfering,measuring and controlling steps only several times when the method ofsymmetrically chamfering a substrate according to the invention isapplied. As the result of the operation carried out, it was possible toreach a desired level of about 50 μm (an average level of 20 μm) bycarrying out the operation 5 times or fewer.

FIG. 9 is a schematic view showing an apparatus of symmetricallychamfering a substrate according to an embodiment of the invention.

As shown in FIG. 9, the apparatus of symmetrically chamfering asubstrate according to an embodiment of the invention includes achamfering wheel, a measuring unit and a controller.

The measuring unit measures an asymmetric chamfering deviation (y) of anedge of a substrate which is chamfered. The controller controls theposition of the chamfering wheel by a function f(y), where the variabley is the asymmetric chamfering deviation.

The foregoing descriptions of specific exemplary embodiments of thepresent invention have been presented with respect to the drawings. Theyare not intended to be exhaustive or to limit the invention to theprecise forms disclosed, and obviously many modifications and variationsare possible for a person having ordinary skill in the art in light ofthe above teachings.

It is intended therefore that the scope of the invention not be limitedto the foregoing embodiments, but be defined by the Claims appendedhereto and their equivalents.

What is claimed is:
 1. A method of symmetrically chamfering a substrate,comprising repeating cycles a plurality of times, each cycle comprising:chamfering an edge of the substrate using a chamfering wheel; measuringan asymmetric chamfering deviation (y) of the edge of the substratewhich is chamfered; and controlling a relative position of thechamfering wheel with respect to a position of the substrate by a valueof a predetermined function f(y) of the variable y, wherein differentsubstrates are chamfered in the respective cycles, wherein in eachcycle, the relative position of the chamfering wheel that was previouslyset is corrected by the value of the function f(y) which is generated inthe respective cycle.
 2. The method of claim 1, wherein the asymmetricchamfering deviation is a difference between a chamfered width of anupper surface of the substrate and a chamfered width of an undersurfaceof the substrate.
 3. The method of claim 2, wherein the relativeposition of the chamfering wheel is controlled to move upward when thechamfered width of the upper surface of the substrate is greater thanthe chamfered width of the undersurface of the substrate, and therelative position of the chamfering wheel is controlled to move downwardwhen the chamfered width of the upper surface of the substrate issmaller than the chamfered width of the undersurface of the substrate.4. The method of claim 1, wherein the relative position of thechamfering wheel is a relative height of the chamfering wheel withrespect to a height of the substrate.
 5. The method of claim 1, whereinthe value of the function f(y) is obtained by multiplying the asymmetricchamfering deviation (y) by a predetermined control constant.
 6. Themethod of claim 1, wherein different substrates are chamfered in therespective cycles.
 7. The method of claim 1, wherein in each cycles, aplurality of the asymmetric chamfering deviations are measured at aplurality of points respectively on the edge of the substrate; and aplurality of the relative positions of the chamfering wheel arecontrolled when chamfering at the plurality of the points on the edge ofthe substrate.
 8. The method of claim 1, wherein the substrate comprisesa glass substrate for a display.
 9. The method of claim 1, wherein thechamfering wheel has a concave groove in an outer surface of thechamfering wheel along a circumferential direction thereof.
 10. Themethod of claim 1, wherein measuring the asymmetric chamfering deviation(y) comprises measuring the asymmetric chamfering deviation (y) using avision camera which detects a chamfered width of an upper surface of thesubstrate and a chamfered width of an undersurface of the substrate.